JPS619020A - Analog-digital converting circuit - Google Patents

Abstract

PURPOSE:To simplify the titled device and to attain ease of operation by inputting an analog signal in common to a control terminal of plural switching elements having different threshold level and extracting the conductive state of each switching element as a 1-bit binary digital signal respectively in parallel. CONSTITUTION:A PNP and an NPN bipolar transistor (TR) Q11, Q12 are used two kinds of switching elements and an analog signal Vi is inputted in common to the two TRs Q11, Q12. Then the conductive state of the one TRQ11 is extracted from the emitter via an inverter L1 as a binary digital signal of H (high level) and L (low level). Further, the conductive state of the other TRQ12 is extracted from the collector via an inverter L2 as the H and L digital signal. Thus, the analog signal voltage Vi is converted into a digital signal output Dout of A, B two-bit parallel type.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a technology that is particularly effective when applied to analog/digital technology and A/D conversion circuits. It relates to effective techniques that can be used to carry out this task.

[Background technology]

For example, in popular type control devices that do not require much precision, analog signals are 2-bit or 3-bit.
It would be convenient to have a simple A/D conversion circuit that can convert into bit-sized digital signals.

In addition, when testing the internal circuit of a semiconductor integrated circuit device by applying a digital signal from the outside, it is possible to partially convert the test digital signal into an analog signal and input it into the semiconductor integrated circuit device. If you convert it back into a digital signal within the equipment and then feed it to the circuit under test.

Advantages such as the ability to reduce the number of signal terminals for the test signals can be obtained.

However, most conventional A/D conversion circuits are highly accurate and large-scale configurations with resolution accuracy of 8 bits or more, and convert analog signals into two
For purposes of simply converting to a bit or 3-bit digital signal, the specifications are extremely excessive. For example, the integrated circuit handbook published by Shokusen Shoten in 1981, pages 222 and 223, describes a follow-up comparison type A/D conversion circuit, but such an A/D conversion circuit is not used for the above-mentioned purposes. Because its structure and operation are too complex, there are a lot of useless elements.
There will be more.

There is also an example of using multiple analog comparison circuits to perform A/D conversion of about 2 or 3 bits, but semiconductor integrated circuits are required to configure the comparison circuits for this purpose. Multiple operational amplifiers were required.

Also, a reference level for comparison operations had to be generated. Therefore, its configuration was quite complex and large-scale. At least, it has not been possible to easily use it in a part of a semiconductor integrated circuit device or in a small-scale device. This has become clear through consideration by the present addressee.

[Purpose of the invention]

An object of the present invention is to be able to efficiently convert an analog signal into a digital signal with a relatively small number of rets using a simple and rational configuration with less waste, and thereby to convert the analog signal into a digital signal with a relatively small number of rets. A/ that is easy to use
I? It provides conversion technology.

What are the above and other objects and novelties of this invention? Regarding the characteristics, please refer to the description in this specification and the attached drawings.
(It will become clear from the y-plane.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, by using a plurality of switching elements with mutually different threshold values, an analog signal can be efficiently converted into a digital signal with a relatively small number of bits with a simple and rational configuration with little waste. This allows A/D to be easily used even in relatively small-scale equipment.
Provides a conversion circuit. This goal is achieved.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

Note that in one drawing, the same reference numerals indicate the same or corresponding parts.

□First, the A/D conversion circuit according to an embodiment of the present invention is as follows:
It is equipped with a plurality of switching elements having different threshold levels, and an analog signal is commonly input to the control terminal of each switching element, and the conduction state of each switching element is expressed in parallel as a binary digital signal of 1 bit each. It was designed to be taken out.

FIG. 1 specifically shows the A/D conversion circuit.

In the A/D conversion circuit 10 shown in the figure, two types of switching elements whose conduction is controlled in a complementary manner with respect to a common analog signal input are used as the plurality of switching elements. More specifically, in this embodiment, the two types of switching elements are a pnp type bipolar transistor Qll and an npn type hexa-Ibora transistor Q1.
2 is used. These two transistors QU1.
The analog signal voltage Vi is commonly input to the base of Q12. One of the pnp bipolar transistors Qll has its emitter connected to the positive power supply Vcc via a load 1 formed of a resistor or a constant current circuit. The collector of the other npn bipolar transistor Q12 is connected to the positive voltage Vcc via a load 1 formed of a resistor or a constant current circuit.

Then, the conduction state of one transistor Q□ is H
' (high level) and 'L'' (low level) as a binary digital signal, which is taken out from its emitter side via inverter L1. Also, the conduction state of the other transistor Q12 is , II H#l (high level) and tgLH (low level) are taken out from the collector side via the inverter L2 as a binary digital signal.Thus, in this embodiment, , the analog signal voltage Vi is converted into a 2-bit parallel type digital signal output Dout of A and B.

Next, its operation will be explained.

In FIG. 1, first, when the analog signal voltage Vi is at the lowest potential, that is, when the two bipolar transistors Q
When it is on the negative side of either threshold value u or t Q x2, only the pnp bipolar transistor qtt is conductive. As a result, the state of the digital signal output Dout is A= , , H, , B == tr L #
The state becomes 1. Next, when the analog signal voltage Vi is at an intermediate potential, that is, on the negative side of the threshold (base-emitter voltage) of the pnp bipolar transistor Qll, and the threshold of the npn bipolar transistor Q12. When it is on the positive side, both transistors Q*x + Q12 are in a conductive state. Digital signal output Dout at this time.

The state is A=It H11, B=”L II.

Furthermore, when the analog signal voltage Vi reaches the highest potential, that is, when it is on the positive side of the threshold of either the pnp bipolar transistor Qut or the npn bipolar transistor Q12, both transistors Q u
Both t and Q12 become conductive. At this time, the state of the digital signal output Dout is A=“H”.

The state becomes B = sr L By. Furthermore, when the analog signal voltage Vi reaches the highest potential, that is, P
When it is on the positive side of the threshold of either the np-type bibonilla transistor Qll or the npn-type bipolar transistor Q12, one transistor Qii becomes non-conductive, while the other transistor Q12 becomes conductive. As a result, the digital signal f signal output Do
The state of ut is A="L#l, 13 == IIH
The state becomes II.

The above operations can be summarized as shown in Table 1 below.

Table 1 (Pair of Vi and A B in 1) As described above, the 2-bit (A, B) parallel digital signal output Dout is A/D converted and output from the analog signal potential Vi. A circuit for performing an A/D conversion operation is constructed very simply, rationally, and without waste using only a small number of switching elements, logic elements, and the like.

Thereby, it can be easily used even in a relatively small-scale device. Also, considering a ternary logic signal as a special case of the analog signal voltage Vi, A according to the system number;
It can be seen that the /D converter is used as a converter from ternary logic to binary logic.

FIG. 2 shows an example of a D/A conversion circuit suitable for use in combination with the above A/D conversion circuit.

The D/A conversion circuit 20 shown in the figure is constructed using 1) npn type bipolar transistors Q3u+Qm having a multi-electrode structure having a plurality of collector electrodes.

A constant current is supplied from a constant current circuit 2 to each base of this transistor QstsQaz. This transistor Q
A constant current Io is supplied from the constant current circuit 2 to each base of the sleQ 32, respectively. Further, a transistor Q2tyQ22 is provided for controlling on/off of the transistor Q3uyQ32.

The switching of these transistors Q2t*Q22 is controlled by digital signals A' and B', respectively.

The above multi-electrode structure npn bipolar transistor Qa
A part of the plurality of collector electrodes of each utQ32 is connected to the base side, and the remaining collector electrodes are commonly connected. Then, the analog signal output Aout is taken out from the common connection point.

Here, one bipolar transistor Q with a multi-electrode structure
The number of collector electrodes connected to the base side of st is the same as the number of collector electrodes connected to the common connection point side. Further, in the other bipolar transistor Q32 having a multi-electrode structure, the number of collector electrodes connected to the common connection point side is twice the number of collector electrodes connected to the base side.
It has doubled. As a result, one transistor 03
The common connection side collector electrode of m can absorb the same current Io as the constant current Io flowing to its base side. In addition, a constant current I flows from the common connection side collector electrode of the other transistor AQ:n to its base side.
It can absorb a current 2Io, which is exactly twice the current 2Io.

Therefore, from the common connection point, the logic signal /l
Current depending on the logic state of A' and B' (maximum I.

+2Io) can be inhaled. As a result, a current sink type analog signal output is output from that common connection point.
can be taken out.

Table 2 below shows the D-/A conversion circuit 20 shown in FIG.
This is an organized representation of the operations.

Table 2 (Comparison table of A', B' and Aout in Figure 2)
As described above, the D/A conversion circuit 20 described above, like the A7'D conversion circuit 10 described above, uses a small number of switching elements, logic elements, and the like.

It is structured very simply and rationally without waste.

As a result, even within a relatively small-scale device, the A/D
Easy to use in combination with conversion circuit 10.
,,can do.

FIG. 3 shows a preferred application example of the A/D conversion circuit 10 shown in FIG. 1 and the D/A conversion circuit 20 shown in FIG.

In the figure, digital test signals A and B from a test device 60 are converted into an analog signal voltage Vi by a D/A conversion circuit 20. This analog signal voltage Vi is
From the test signal input terminal TPI to the semiconductor integrated circuit device 50
entered within. And the semiconductor integrated circuit device i5
The digital test signals A and B are returned to the original digital test signals A and B by the A/D conversion circuit 10 in the semiconductor integrated circuit device 50, and are applied to the circuits under test 31 and 32 in the semiconductor integrated circuit device 50, respectively. Test output signal A from the circuit under test 31', 32.

B' is the D/A conversion circuit 2 in the semiconductor integrated circuit device 50.
0, it is once converted into an analog signal output Aout. This analog signal output Aout is the test output terminal T.
External A/D conversion circuit 10 led out from P2
is input. Then, this external A/D conversion circuit 10 converts the digital signal A'.

It is converted into B' and input to the test device 60 as a test result.

In the above manner, for example, two test terminals TPI,
With TP2, a test function equivalent to using four test terminals can be obtained.

This allows the number of terminals of the semiconductor integrated circuit device 50 to be reduced.

FIG. 4 shows another embodiment of the A/D conversion circuit according to the present invention.

The A/D conversion circuit 10 shown in the figure includes a P-channel MO8 field effect transistor QU as the switching element.
It uses a t and n channel MO8 field effect transistor Q12. With this circuit as well, effects similar to those shown in FIG. 1 can be obtained.

FIG. 5 shows a digital signal A output from the A/D conversion circuit IO shown in FIG. 1 or 4.

B to alternative selection signals X'l, X2 . An example of a decoder that creates X3 is shown.

In the degoder shown in the same figure, first, inverters LL, L2
The digital signals A and B are divided into positive logic and negative logic signals using
Gate L3. The signal is guided to L4° and L5, and a decoding operation is performed. As a result, only one output of the selection signals Xi, X2 . X3 is obtained.

[Effects] (1) A plurality of switching elements having different threshold levels are provided, and an analog signal is commonly input to the control terminal of each switching element.

By extracting the conduction state of each switching element in parallel as a binary digital signal of 1 bit each, it is possible to convert analog signals into digital signals with a relatively small number of bits using a very simple and rational configuration with little waste. It is possible to efficiently convert the signal into a signal, thereby providing an effect that an A/D conversion circuit that can be easily used even in a relatively small-scale device can be obtained.

(2) Furthermore, by providing the A/D conversion circuit in a semiconductor integrated circuit device having test terminals, it is possible to reduce the number of test terminals of this semiconductor integrated circuit device. .

Although the invention made by the present inventor has been specifically explained above based on examples, it is to be understood that this invention is not limited to the above-mentioned examples and can be modified in various ways without departing from the gist thereof. Not even. For example, a configuration may be adopted in which three or more of the above switching elements are used. Further, the threshold level of the switching element may be adjusted using, for example, the forward effect voltage of a diode.

As a result, three or more types of switching elements having mutually different threshold levels can be obtained, and it is therefore possible to configure a circuit that performs an A/D conversion operation of three or more bits.

[Application field]

The above explanation will mainly focus on the invention made by the present inventor in the field of application, which is the background of the invention.
Although the description has been made regarding the case where the present invention is applied to testing technology for integrated circuit devices, it is not limited thereto; for example,
It can also be applied to modulation and demodulation technology in data communications. It can be applied at least to conditions where information expressed in analog quantities is expressed in digital quantities.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an A/D conversion circuit according to the present invention, and FIG. 2 is a circuit diagram showing an example of a D/A conversion circuit suitable for use in combination with the above A/D conversion circuit. Figure 3 is above A.
FIG. 3 is a block diagram showing a preferred application example of the /D conversion circuit. FIG. 4 is a circuit diagram showing another embodiment of the A/D conversion circuit according to the present invention, and FIG. 5 is a decoder that creates a selection signal from the output of the A/D conversion circuit shown in FIG. 1 or 4. It is a circuit diagram showing an example. l...load, 2...constant current circuit, Vcc...power supply, Qlm...switching element (pnp type bipolar transistor or one channel MO8 field effect transistor), Qm* switching element (npn type bipolar transistor or n channel 9MO8 field effect transistor), 10... A/D conversion circuit, 20...
・D/A conversion circuit, Qal, QH...n of multi-electrode structure
pn type bipolar transistor, Vi...analog signal voltage, Dout...digital signal output, Aout...
. . . Analog signal output, 50 . . . Semiconductor integrated circuit device, 60 . . . Test equipment, LL, L2 . . . Inverter, L3. L4. L5...AND gate. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. An A/D conversion circuit that converts an analog signal into a digital signal, comprising a plurality of switching elements having mutually different threshold levels, and having a common analog signal to the control terminal of each switching element. What is claimed is: 1. An A/D conversion circuit characterized in that the conduction state of each switching element is input in parallel as a binary digital signal of 1 bit each. 2. The A/D conversion circuit according to claim 1, wherein the plurality of switching elements are comprised of two types of switching elements whose conduction is controlled in a complementary manner with respect to a common analog signal input. . 3. A semiconductor integrated circuit device having a test terminal, comprising an A/D conversion circuit for converting an analog test signal inputted from the test terminal of the semiconductor integrated circuit device into a digital test signal; A digital test signal is applied to the circuit under test in the semiconductor integrated circuit device, and a D/A conversion circuit is provided for converting a test output signal from the circuit under test into an analog signal. A semiconductor integrated circuit device, characterized in that an analog signal from a conversion circuit is led out from a test terminal of the semiconductor integrated circuit device.